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The Ca C[H.sub.3]F reaction CaFC[H.sub.3] reaction is studied experimentally and theoretically. An alternative reaction mechanism involving a transfer to triplet potential energy surfaces is proposed.

The transition state of the reaction, [Ca.sup.*] + C[H.sub.3]F --> Ca[F.sup.*] + C[H.sub.3] was photoinduced in 1:1 Ca...C[H.sub.3]F complexes formed in a supersonic expansion, and were examined by monitoring CaF while scanning the laser that turns on the reaction. Experimental results for the free complex and a comparison with the results of a previous experiment where the Ca...C[H.sub.3]F complexes are deposited at the surface of large argon clusters are presented.

The dynamics of the photoinduced reaction producing electronically excited CaF when 1:1 Ca.CH(sub 3)F complexes are deposited at the surface of large argon clusters are examined using the 'cluster isolated chemical reactions' technique. The observations suggest that a profound alteration of the calcium electronic structure and a control of the reaction by the CF stretch in CH(sub 3)F.

A combination of the gas-phase laser spectroscopy and quantum chemistry approaches is employed to explain the properties of a two-residue model peptide. The application of the technique in explaining the different dispersive interactions is also explained.

The observation of reactions in the ionic monomer and the ionic multimers of the title molecule, tetrakis-(dimethylamino)ethylene (TDMAE) resulting in the formation of several ionic products are reported. The ion molecule reactions via femtosecond excitation and ionization of [Tetrakis(dimethylamino)ethylene] are investigated.

The Fregeneda-Almendra pegmatite field of the Iberian Massif represents a typical expression of peraluminous rare-metal magmatism that occurred over western Europe at the end of the Variscan orogeny. It is the host for two main types of Li-mineralized intrusions, identified at the scale of the Variscan belt, including petalite- or spodumene-rich pegmatites, as well as Li-mica-rich pegmatites, for which the origin of mineralogical-chemical differences is not yet understood. Here, we provide cassiterite and columbite-group mineral (CGM) U-Pb ages along with oxide, mica and phosphate mineral compositions for Li-pegmatites from the Fregeneda-Almendra field in order to assess their petrogenesis and tectonic-magmatic context of emplacement. U-Pb geochronology indicates that petalite-rich and Li-mica-rich pegmatites were mostly emplaced sub-synchronously from 315 ± 6 to 308 ± 6 Ma, during strike-slip deformation and granitic magmatism within an anatectic dome bounding the pegmatite field. U-Pb data and pegmatite geographic zonation suggest that Li-pegmatites were sourced from buried equivalents of leucogranites and migmatites from the dome. Li-pegmatites experienced a complex crystallization including K-feldspar, petalite, topaz, Nb-Ta-Fe-Mn-rich cassiterite, amblygonite-group minerals (AGM) and CGM as early magmatic phases, followed by lepidolite for Li-mica-rich pegmatites. At the magmatic-hydrothermal transition, notably leading to the formation of Nb-Ta-Mn-Fe-poor cassiterite hosting CGM inclusions, earlier minerals were resorbed by muscovite and albite. A later F-rich hydrothermalism is locally reflected by zinnwaldite overgrowths on muscovite. Cassiterite, CGM and micas from petalite-rich pegmatites show lower Mn/Fe ratios and higher Ti contents, along with lower Zr-Ga contents for cassiterite, than that from Li-mica-rich pegmatites. Such behavior is consistent with a magmatic differentiation process whereby Ti content decreased and the degree of Mn-Fe geochemical fractionation and solubilities of Ga and Zr increased in the melts, possibly in relation with high fluorine activity. In Li-mica-rich pegmatites, AGM equilibrated with a melt with up to 2 wt% F, similar to that in equilibrium with lepidolite (1–3 wt%). In petalite-rich pegmatites, the relatively high F concentration of the melts equilibrated with AGM (≤ 1.5 wt% F) contrasts with the liquid equilibrated with muscovite (< 0.5 wt% F). This can be accounted for by muscovite crystallization after the exsolution of a F-rich aqueous phase at the magmatic-hydrothermal transition. Relatively similar F contents in the initial melts of petalite- and Li-mica-rich pegmatites support the hypothesis that the stability of lepidolite does not only involve high F but also a low H2O/F activity ratio. For the Fregeneda-Almendra Li-mica-rich pegmatites, this could be explained by a decrease of melt H2O solubility due to a relatively low pressure of emplacement.